The prior art has contemplated a multitude of bar pullers and magnetic holders or the like, although none are believed to contemplate, teach, or otherwise suggest the device of the present invention.
A list of patents which may have some pertinence to the present invention include:
U.S. Pat. No. Inventor Date of Issue 2915682 Bower 12/01/1959 3010054 Goudsmit 11/21/1961 3079191 Engelsted et al 02/26/1963 4401960 Uchikune et al 08/30/1983 4924738 Che 05/15/1990 5080380 Nakagawa et al 01/14/1992 5115702 Link 05/26/1992 5165313 Karr 11/24/1992 5845950 Stowe et al 12/08/1998 5960689 Warren 10/05/1999
U.S. Pat. No. 3,079,191 dated Feb. 26, 1963, teaches a "Permanent Magnet Lifting Device" including a housing having first and second ends, the first end configured to engage a support, the second end configured to form the work piece engagement end. The housing has formed therethrough a bore having slidably situated therein, a magnet housed in a piston (in this case, two bores and two pistons), with a magnetic surface facing the second end of the housing. A cap is provided at the second end to form a work piece contact surface. Further provided is means to motivate the piston/magnet arrangement within the bore to and away from the work piece contact surface at the second end of the housing, so as to engage/disengage the work piece.
U.S. Pat. No. 2,915,682 issued 1959, which also includes spring (30) to provide spring bias to the system. Another example may be found in 4,401,960, entitled "Magnet Assembly". Lastly, U.S. Pat. No. 5,845,950 teaches a "Pneumatically Actuated Magnetic Article Holder" having some relevance to the above patents, but teaching fluid actuation to motivate the magnet means.
The above patents are distinguishable from the present, searched for invention, as they do not teach a bar puller, although it is possible that one or more of the above devices might be able to be modified to perform as such. For other magnetic holders, see U.S. Pat. No. 5,080,380 for a "Magnetic Chuck" assigned to Murata Manufacturing, Inc., teaching multiple pistons in a housing, the pistons forming magnets, which are motivated to move to and from a work piece surface via compressed air. This patent is relevant in that, in addition to the concept of providing a work piece holder utilizing a piston having a magnet which is motivated to and away from the work surface, this patent also teaches the concept of utilizing fluid pressure to accomplish same.
U.S. Pat. Nos. 4,924,738, 5,165,313, and 5,960,689 provide examples of bar puller patents.